Calcium chlorate-calcium chloride mixed product



Patented Feb. 12, 1935 UNITED STATES' PATENT OFFICE CALCIUM CHLORATE-CALCIUM CHLORIDE MIXED PRODUCT Sheldon B. Heath, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Michigan No Drawing. Application June 17, 1931, Serial No. 545,152

4 Claims. (01. 167-45) The present application has reference to a the molten salt on a cooled moving metallic surnew and improved product consisting of a mixface and scraping it off, because the flakes are 'ture of calcium chlorate and calcium chloride in soft and moist and tend to pack together in the flake or similar subdivided form, such product same manner as the crystals.

5 being particularly adapted for use as an herbi- Ihave found, however, that by adding a limited 5 cide and the like. amount of calcium chloride to the moist calcium It is well known that chlorates are effective chlorate crystals and melting or dissolving the agents for destroying vegetation, being used parmass to form a homogeneous mixture, the latter ticularly as weed killers and the like, usually by upon further evaporation may be readily flaked spraying a solution of the chloride upon, the vegein the form of strong, hard flakes which are free- 10 tation which it is desired to eradicate. One danflowing and non-caking, and are especially well ger connected with such use, however, has been adapted for packaging and storing. A further found to exist in the extreme inflammability of advantage is that the flaked mixed product so the dead and dried up foliage which is more or prepared contains approximately the optimum less impregnated with the chlorate. To avoid proportions of chlorate and chloride which have 15 this danger it has been proposed to employ a been found suitable for use as an herbicidal comhygroscopic salt in combination with the chlorate, position.

so that the dead vegetation may be kept moist by The raw crystals of calcium chlorate as ohthe absorption of water from the air by the hytained by the process of the aforesaid Patent groscopic salt and hence less liable to take fire. No. 1,887,809 by centrifuging but without wash- 0 'Calcium chlorate, for example, is eifective and ing contain a small amount of calcium chloride economical as an herbicide, and a mixture of due to the adhering mother liquor. An average calcium chlorate and calcium chloride has been analysis of such crystals is;

found well adapted to furnish the required com- Per cent bination of an herbicidal agent and a hygroscopic Ca(ClO 2 79 25 salt. It is desirable to provide such mixed prod- CaCl2 6 uct in a free-flowing, subdivided form which is H2O 15 economical to manufacture, convenient for pack- I aging, storing or if pensing d not subject to Crystals of such composition, 1f melted up, evap an orated and flaked, do not produce a hard flake. 30 deterioration due to cakmg 1n the package. The

. However, if sufficient calcium chloride is added invention, then, consists in the new product, to-

- thereto to make a mixed product having a chlo gether with the method for preparing the same, mt e ch1 on de ratio between hereinafter fully described and. particularly pointed out in the claims. 55 In my prior application erial No. 424,493, filed i5 35 January 30, 1930 now Patent No.l,887,809, I have d disclosed a method of crystallizing calcium chlo- 5 rate in the form of the dihydrated salt, T

Ca(Cl0a)2.2HzO, from solutions thereof containing also calcium chloride. The raw crystals y W t of the anhydrous Salts, d the molten 40 thus obtained constitute a moist, soggy, deliquessa t mi tu is vap rated until a slurry f y cent mass which, while it does not harden to a, tals and mother liquor is formed containing from solid cake, is not at all free-flowing and liquefies 6 12 p t o Wat Such Slurry may be readily if moderately heated. These crystals fl d t p e a Strong, hard fl which 5 cannot be surface dried by any ordinary method is free-flowing and will withstand mechanical in order to render them free-flowing since upon handling W thout, materially dlsmtegratm heating to a temperature between about 60 and p v 67 C. they melt in their water of crystallization As an example of the preparation of a mixed without drying. The molten dihydrate may be product of the character in question, a solution 5 further evaporated and the anhydrous chlorate is provided containing approximately 77 parts crystallized at a temperature above 67 C., but Ca(ClO3)z to 23 parts CaClz by weight, and such procedure involves tedious manipulation and evaporated until a sufflcient amount of crystals necessitates disposing of the mother liquors. It is formed to produce a hot slurry of such conhas not been found practicable to flake the salt in sistency as may still be handled by a centrifugal the well known manner by solidifying a layer of pump. The evaporation temperature should not 56 be allowed greatly to exceed 160 C., inasmuch as above such temperature decomposition of chlorate may occur, accompanied by evolution of oxygen and chlorine. In order to enable the evaporation to proceed far enough at a temperature below 160 C. to produce a suitable crystal slurry, the evaporation is carried "out, or' at least finished, under reduced pressure, e. g. at approximately 10 to 12 inches of mercury absolute pressure. Under such regulated vacuum, accordingly, the evaporation is continued until the temperature of the liquor rises to about 160 C. The hot crystal slurry so formed is then transferred to the trough or pan of a flaking apparatus wherein it is contacted with the surface of an internally cooled revolving metallic drum or cylinder. A thin film of the salt mixture is solidified on the drum surface, and then scraped therefrom to form flakes, in the well known manner. The solidified film is hard and brittle and is detached easily from the surface by the scraper, forming strong flakes which are free-flowing and non-caking. The flakes scraped from the drum are preferably aircooled to about room temperature and may then be packaged, exhibiting in storage thereafter no tendency to cake in a tight package which is closed against the entrance of air, even when exposed to temperatures as high as 100 C. The product so prepared has an analysis approximately as follows;

.. Per cent Ca(ClO3)'z CaCh l.. 21 H20 9 Naturally the analysis may be varied within the limits already stated, depending upon the actual proportions of calcium chlorate and calcium chloride in the original solution employed.

The crystals produced in the hot liquor during evaporation are probably of calcium chloride monohydrate, C8C12.H20. An advantage of continuing evaporation until a crystal slurry is produced, is that such slurry sodifies more quickly than a clear hot solution of the two salts, and does not adhere tenaciously to the surface of the flaker drum, so that it can be more easily and rapidly flaked. If desired, the flakes may be surface dried by contacting with a hot gaseous current, in accordance with the general method disclosed in United States Patent No. 1,527,121.

While particular advantages are realized in preparing a flaked mixed product according to the procedure hereinbefore described, at least some of the advantages are retained when, instead of flaking, the crystal slurry is chilled and solidified mechanically by means adapted to produce a granulated product according to methods .familiar to those versed in the art.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the method herein disclosed, provided the step or steps'stated Many of the following claims or the equivalent of such stated step or steps be employed.

I therefore particularly point out and distinctly claim as my invention:-- 7 1. The method of making a calcium chloratecalcium chloride mixed product which comprises preparing a solution of the two salts containing from 65 to parts of such chlorate to from 35 to 15 parts of such chloride, evaporating the same to a temperature not materially exceeding C. to produce a slurry of crystals and mother liquor thereof containing from about 6 to about 12 per cent of water, chilling and mechanically sub-dividing such slurry to solidify the same in the form of small particles.-

2. The method of making a calcium chloratecalcium chloride mixed product which comprises preparing a solution of the two salts containing from 65 to 85 parts of such chlorate to from 35 to 15 parts of such chloride, evaporating the same to a temperature not materially exceeding 160 C. to produce a slurry of crystals and mother liquor thereof containing from about 6 to about 12 per cent of water and flaking such slurry.

3. A composition of matter comprising partially hydrated solid flake or granular particles composed of calcium chlorate and calcium chloride in the ratio of the former to the latter between a 15 and by weight, containing from 6 to 12 per cent of'combined water, such particles beinghard,

free-flowing, and not subject to caking in storage.

by weight, and containing from 6 to,12 per cent of combined water, such particles being hard 55 

